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CO2 geological storage (Carbon Capture and Storage - CCS)

The European Commission has set up several initiative aimed at the implementation and application of the CCS Directive for the member States. Since 2003, OGS is involved as coordinator and partner in several projects on the CO2 geological storage, thanks to its great expertise in the geophysical exploration (decade-long activities on the energy sector for Eni, ENEL, ENEA) and to consolidated collaborations with the main European Institutions involved in geo-energy studies.

OGS activities fit completely with the European strategy related to climate and energy challenges, which Europe intends to pursue with the aim to achieve a Low-Carbon Economy in 2050.

OGS primary activities for the next three years can be summarized as follows:

 

Identification and characterization of sites potentially suitable of CO2 geological storage

CO2 geological storage represents one of the leading research activities that OGS has developed thanks to its involvement and leadership in several European projects. In particular, the reconstruction of the geological-structural model (static model) represents the first step in the characterization of a reservoir potentially suitable for CO2 storage. To provide this model, OGS adopts a procedure widely used in the framework of several European projects, where the following steps are established to properly select the injection site:

  • analysis of the borehole data at a local and regional scale, represented by composite logs, containing information on lithology, formation ages, biofacies associations, geophysical logs, pressure and temperature, petrophysical information;
  • analysis of the available 2D and 3D multichannel seismic profiles, which could be also re-processed with an OGS dedicated software. Data interpretation plays a crucial role since it allows to identify tectonic structures which could compromise the integrity of the storage complex.

 

3D modelling to evaluate the behaviour of the injected CO2

The next step in the characterization of a CO2 storage site is represented by the building of the 3D geological/structural model, as a result of the seismostratigraphic and structural interpretation, where the sequence boundaries and the main fault/fracture systems are identified. Then, the volumetric gridding of the geological/structural model, both at a regional and at a local scale is built. Different cell size are commonly used, i.e. a more thin gridding is created for the reservoir formation in order to provide a better resolution of its characterisation. The volumetric gridding represents a crucial step for further modelling activities, like geomechanical and fluidodynamic simulations.

 

Geophysical monitoring of a CO2 storage site

OGS has developed a petro-elastic numerical methodology to compute realistic synthetic seismograms and is able to analyze the sensitivity of the seismic response when injecting CO2 in a depleted gas reservoir and in an aquifer. The methodology has been used to assess the sensitivity of the seismic method to detect the CO2 plume and possible CO2 leakages at several European sites where CO2 injection is taking place. In particular, OGS considers rock-physics models to characterize the reservoir before the injection of CO2, computes the seismic properties of the mixture of brine and carbon dioxide at in situ conditions and performs a fluid substitution procedure. OGS also performed the attenuation tomographic inversion of a 2D seismic line collected in the Sleipner project area in 2006 and made the comparison with a coinciding profile from 1994 baseline seismic data set. The analysis gave a multi-parameter model (velocity and seismic quality factor Q) that was compared with the corresponding multi-parameter obtained from the baseline 1994 seismic data. The change both in velocity and attenuation as a consequence of CO2 injection is evident.

 

OGS as member of the Observatory on the Carbon Capture and Storage (Osservatorio CCS)

 The Observatory on the Carbon Capture and Storage is promoted in Italy under the initiative of the Sustainable Development Foundation. The Observatory is an expert and independent forum for the promotion of CCS in Italy. The Observatory is formed by technologists and researchers of the Economic Development and Environment Ministry, ENEL, ENEA, ENI, ISS, INGV, OGS and the Rome and Florence Universities. The Observatory gathers information and documentation on the technological aspects of CCS, on the development of research and its applications and on the ongoing projects at European and international level. OGS activity within the Observatory is related to the transposition of the EU Directive of CCS in implementing decrees.